I've been booking through Orbitz rather than through NW's website because I can get the schedule times I need. NW will allow you to pick and choose, too, but the total price usually comes out a little higher. Orbitz adds a service charge, but overall they're about a wash. Also, NW always seems to list exactly 16 possibilities -- maybe it's just my itin, but it seems there's always 16 choices.

Orbitz also lets me construct a flight using partners (like America West) which will earn me NW miles but which I can't book on nwa.com. Or maybe I can, but I just don't know how.

I've never used either Expedia or Travelocity. The latter, I hear, is the mileage runner's friend, but i'm not into that (at least not yet ). Still, I'd like to know if I should switch to one of these services rather than Orbitz.